Kirtland Air Force Base outside Albuquerque went on lock down after someone called 911 after hearing three large banging noises, base officials said. Tensions were running high after last week’s mass shootings in San Bernardino, California.

“One individual had some heavy-duty bubble wrap and was stepping on it to pop it,” Eric Elliott, the base’s public affairs officer told the Albuquerque Journal.

Three nearby schools and the base were on lockdown for about 45 minutes.